1. Field of the Invention
With reference to the classification of art as established in and by the United States Patent and Trademark Office, the present invention is believed to be found in the general class entitled, "Mining or in Situ Disintegration of Hard Material" (Class 299) and in the subclass entitled, "expansible breaking down devices-piston" (subclass 22) and the subclass using a "wedge" (subclass 23).
2. Description of the Prior Art
The use of a wedge and associated feathers for splitting rock is shown particularly in U.S. Pat. No. 3,957,309 to DARDA as issued on May 18, 1976 and in U.S. Pat. No. 4,114,951 as issued Sept. 19, 1978 to LANGFIELD, et al. These references are applicable to a hydraulically actuated rock splitter in which a tapered wedge is moved between opposed and contiguous feathers. Conventionally, the upper ends of these feathers are retained by housings of metal. On the thrust and splitting movement or action of the wedge there is a thrust load on the enlarged retaining ends of the feathers. This thrust load is conventionally transmitted by and through hardened steel plates to a housing retainer.
As reducer to practice, this hardened steel thrust or wear plate often cracks or breaks during or as a result of the thrust and splitting action movement of the tapered wedge. These wear or thrust plates are retained by grooves and/or screws. Under this thrust and when and where dirt, a rock or other material or factor reduce the ability of the wedge to slide along the face of the feathers an increase of pressure and a cracking or breaking of these wear plates results. Repeated actuation of the wedge to produce a splitting action often causes the cracked or brokenwear or thrust plates to cut or mutilate the housing or retainer, usually made of aluminum, to the extent that it is not satisfactorily useable.
In particular the housing or retainer used in th DARDA apparatus and as shown in the LANGFIED patent above identified utilizes an aluminum alloy. The wear or thrust plates are hardened steel and when broken or cracked the sharp edges of said wear plates cut or gouge portions of the retainer. Repeated use of the tool often causes the area of the housing retaining these broken wear plates to become cut or worn beyond accetable limits. The present invention provides an additional thrust plate of soft steel which may be bonded to the hardened steel plate by epoxy cement, silver soldering or brazing. In certain installations or applications the soft metal plate may be held in place by pins or screws and the hardened steel plate placed next to the softer steel plate. This results in the hardened steel plate being positioned between the soft steel plate and the enlarged end portions of the feathers.
When damage to the housing occurs from the cracking and further disintegration of the broken thrust plates takes place because of continued use of the rock splitter, repair of the housing is required. This rework of the housing occurs at the recess where the thrust plate is originally mounted. This rework consists of remachining of this recess to accommodate the additional thrust plate of softer steel. If the damage to the housing is extensive, a cutting away of the damaged portion may weaken the housing to a degree that is unsatisfactory. The housing then must be discarded or a rebuilding of the damaged area may be accomplished by welding and remachining.
The softer steel support plate is preferably made as one-quarter, five-sixteenths, three-eighths or sometimes as much as seven-sixteenths inch in thickness. This does not preclude a thickness of up to three-quarters of an inch which has proven satisfactory. The same contour on the outside as the hardened thrust plate is usually carried forth in the softer steel reinforcing support plate, to be hereinafter more fully described.